I don’t know if this help you and if I understood what you need.
You want a point from the SURFACE of the bounding box instead
a random point of the VOLUME?
What about this:
put a cube in the location of the bounding box and same dimmensions
The cube is just to generate a trace hit.
Then you make a trace by channel from a random place of the outside to the center of the cube…something similar to this:
